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Robert Diaz

The Lidocaine Killer


Robert Diaz

Robert Diaz

Robert Diaz was an American serial killer that used his position as a nurse to gain access to his victims. In March and April 1981, he murdered at least 12 hospital patients. His victims, both men and women, ranged in ages from 52 to 89. His choice of weapon was the drug lidocaine.

Childhood Years

Robert Diaz, also known as David Robert Diaz, was born in Gary, Indiana in 1938. He grew up in a large, poor family, but managed to capture the attention of his parents with the many illnesses he suffered throughout his younger years. Because he was frequently ill he also missed a lot of school and only completed 10 grades before dropping out.

At the age of 18 Diaz joined the Marines, but he was unable to adapt. He was later discharged after going AWOL for six weeks.


Diaz' first marriage was from 1961 until 1972. It is believed that he fathered at least one child, a son, during that marriage.

With his military career and marriage over, Diaz decided to pursue a lifelong goal of getting into the field of medicine. As a child he had dreamed of being a doctor one day, but he was never encouraged by his parents to pursue it.

Although his dreams of becoming a doctor never worked out, he did manage to earn a position as a vocational nurse.

Egyptian Royalty

Diaz showed early signs of having an inflated opinion of himself. He told people that he was reincarnated and in his previous life he was an Egyptian mystic born from royalty. The need for him to appear to others as something greater than he could obtain seemed to be an underlining force throughout his life.

When he began working as a nurse he insisted that his family refer to him as "Dr. Diaz" even though he clearly lacked the credentials to warrant the title.

Diaz also felt that he could use mind control over his cat and would sit, staring at the cat for hours at a time.

Graveyard Shifts

In 1981, Diaz worked through a temporarily employment agency which placed him in various hospitals in counties all around Riverside County in California, usually to work graveyard shift. Immediately the number of older patients dying noticeably increased. Many of the patients dying were not considered critical cases which raised the suspicions of hospital administrators.

An investigation was launched and in several of the cases the coroner found high levels of lidocaine in the tissue of the deceased patients. Lidocaine is used to regulate heartbeats, but when administered in too high a dosage the outcome can be lethal. The dosage found in patients was up to 2,000 milligrams. The normal licodcaine dosage is 50 to 100 milligrams.

Authorities and hospital administrators knew that they were now dealing with a serial killer who was likely an employee.

An anonymous tip into the San Bernadino County coroner named Diaz as being responsible for several of deaths. Investigators took notice and began piecing together timelines. It did not take long to determine that Diaz was somehow involved in the suspicious deaths.


At the Community Hospital of the Valley in Perris, California, there was a 12-day span when several patients died suspiciously. Diaz had worked 10 of those shifts. He also worked one shift at the San Gregorio Pass Hospital in Banning when another patient died due to an overdose of lidocaine.

Co-workers told investigators that Diaz had an uncanny ability to predict when some of the patients would die and even went as far as suggesting that co-workers schedule their breaks based on his predictions. Diaz was also seen giving injections to patients prior to their deaths.

The investigators had enough evidence to get a search warrant for Diaz' home. There they found several bottles of lidocaiene and morphine, as well as syringes containing lidocaiene that were labeled with some of dead patient's names. Many of the lidocaiene syringes were also labeled as being a lower dosage than what they contained.

First-Degree Murder

On November 24, 1981, Diaz was arrested and charged with murdering 11 patients at the Community Hospital of the Valley and one patient at the San Gregorio Pass Hospital.

Bench Trial

Against the advice of his attorney, Diaz opted for a bench trial rather than being judged by a jury.

When presented with the evidence Diaz explained that the syringes found in his home were there because he would forget to remove them from his pockets when leaving work. He never explained or admitted to why he tampered with the amount of lidocaine inside the syringes.

He said a patient's deteriorating condition is how he could predict their deaths and blamed hospital doctors for not properly attending to the patients.

Judge John J. Barnard found Diaz guilty on all counts and on March 29, 1984, he was sentenced to die and was sent to San Quentin to await execution.

Drug of Choice

Had Diaz lived long enough to be executed he would have likely been injected with increased dosages of various drugs, including his drug of choice - lidocaine. However, in August 2010, Diaz died of natural causes 26 years after his conviction.
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